System modular unit having a potentiometer switch arrangement for tuning devices of hf-communication transmission apparatus

ABSTRACT

A modulator-switch unit for use with tuners for HFcommunications equipment contains a potentiometer consisting of a resistance element and a slider arranged on a tuning spindle disposed within a housing and provided with a pushbutton. The pushbutton is slidably supported within the housing parallel to the tuning spindle and is employed to actuate the switches so that the potentiometer may be connected to a desired tuned circuit by way of connecting studs projecting from the bottom of the housing.

United States Patent Inventors Appl. No.

Filed Patented Assignee Priority Peter Hengstler' Deisslingen;

Lothar Volkheimer, Trossingen, both of, Germany Feb. 4, 1969 June 1, 1 97 1 R. 81 E. Hopt KG Auf der Breite, Germany Feb. 9, 1968 Germany SYSTEM MODULAR UNIT HAVING A POTENTIOMETER SWITCH ARRANGEMENT FOR TUNING DEVICES OF HF-COMMUNICATION TRANSMISSION APPARATUS 22 Claims, 9 Drawing Figs. US. Cl 338/179, 334/53, 338/129, 338/133, 338/200 Int. Cl Hlc 9/08, HOlc /08 [50] Field of Search 200/ 16; 334/5254;335/135, 159; 338/128, 129, 176, 179, 180, 198,200, -133, 137-440, 142,

Primary Examiner-Lewis 1-1. Myers Assistant Examiner-Gerald P. Tolin Attorney-Craig, Antonelli, Stewart and Hill ABSTRACT: A modulator-switch unit for use with tuners for PIP-communications equipment contains a potentiometer consisting of a resistance element and a slider arranged on a tuning spindle disposed within a housing and provided with a pushbutton. The pushbutton is slidably supported within the housing parallel to the tuning spindle and is employed to actuate the switches so that the potentiometer may be connected to a desired tuned circuit by way of connecting studs projecting from the bottom of the housing.

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sumanrz INVENTORS mm GSTLt'R mvn LOTMR munEzmER ATTORNEYS SYSTEM MODULAR UNIT HAVING A POTENTIOMETER SWITCH ARRANGEMENT FOR TUNING DEVICES OF HF-COMMUNICATION TRANSMISSION APPARATUS The present invention relates to a construction unit, or basic unit, for tuners for HF communications equipment, in particular for television and radio receivers, with a potentiometer consisting of a resistance element disposed in a housing and a slider disposed on a tuning spindle supported in the housing and with a pushbutton slidably supported in the housing parallel to said tuning spindle, said pushbutton being used to actuate switches by means of which said potentiometer may be connected to a tuned circuit, said switches being provided with connecting studs projecting from the bottom of the housing.

Similar construction 'units for assembling tuners have been suggested prior to this invention. In these previously suggested construction units the switches are formed by contact springs disposed transversely to the direction in which the pushbutton moves, the free ends of said contact springs being located in the way of projections on the pushbutton which are removed from, or applied against, corresponding cooperating contacts when the button is depressed. In the known construction units, these cooperating contacts are also formed by elongated contact springs, It is obvious that in;an arrangement of this typev the contact springs must be adjusted very carefully to ensure proper perfonnance, in particular where a major number of switches are to be disposed in linear succession one behind the other. The spring-type contacts must also have a certain length, with the result that such construction units are necessarily comparatively large-sized. Furthermore, the suggested construction unit is characterized by a relatively complicated design and poor adaptability accounted for by the fact that the pushbutton takes the form of a rod, that a tuning knob for the tuning spindle is supported on the pushbutton, and by the magnet arrangement selected for retaining the pushbutton in its depressed position.

The suggested constniction unit is considerably improved and simplified by the present invention. The invention consists in that the connecting studs are disposed in two rows parallel to the pushbutton and provided with short ends projecting into the interior of the housing, said ends serving as direct switch contacts, and in that the pushbutton is formed by a slide running along the bottom of the housing, said slide featuring a section entering between the ends of the connecting studs and having inserted in it contact springs disposed transversely to said slide which in one of the two positions of the pushbutton connect the ends of contact studs arranged in opposite pairs in both rows.

A well-defined correlation of contacts which cannot be disturbed by external influences and completely eliminates any erroneous contact-making is achieved by using the stud ends as contacts and employing a slide with inserted contact springs. It is impossible to distort the contacts or produce any other disturbances even by interfering, in a careless manner, with the interior of the housing. Consequently, there is no risk involved in keeping the housing open on one side so that it may, for instance, take the form of an injection-moulded plastic part with one open side. A cover for the open side can then be dispensed with. In addition, improved possibilities of actuating the pushbutton and locking it in the depressed position result from the fact that the pushbutton takes the form of a slide supported in the housing in a manner preventing it from rotating and provided with surfaces which can be readily adapted for cooperation with further elements or which may be provided with such further elements. The pushbutton, too, may be fabricated from plastic in a simple fashion by a compressionor injection-moulding process.

In a preferred embodiment of the invention, the contact springs take the form of essentially V-shaped bent leaf springs inserted in an upright position, i.e. on edge, in recesses of the slide which are open towards the bottom of the housing. At their apices, these contact springs are restrained from both sides, while the ends of their legs, which are continued by retaining tabs bent off in an inward direction, project through slots in webs forming the boundaries of the recesses on either side and entering between the rows of stud ends. Accordingly, in this embodiment of the invention, the contact springs are formed by leaf spring sections, which are simply inserted in corresponding recesses of the slide and, on account of their shape, ensure excellent contact.

In a further embodiment of the invention, the slide may be provided, at least at one edge, with a web extending over the row of studs. In this case, a pressure mechanism which locks the slide in its depressed position against the force exerted by a spring and releases it again in response to a further application of pressure may be disposed between the outer surface of this web and the adjacent wall of the housing. This means that the slide of the construction unit according to the invention takes the form of a reset button, and a mechanism of the type known from retractable-tip ball point pens or the like may be provided to lock the button.

A particularly simple embodiment of such a pressure mechanism consists of an arm hinged to the outside of the web of the slide, said arm extending from its pivot to the rear end of the slide and being provided, at its free end, with an outward projection entering into a guide slot defining a heartshaped curve in the sidewall of the housing. The guide slot can be injection-moulded integral with a plastic housing without any difficulty, while a particularly simple form of the arm consists of a piece of wire bent off at its two ends in opposite directions, one of these bent-off ends extending into a bore in the web of the slide and the other end entering into the guide slot. Consequently, both manufacture and assembly of this pressure mechanism are extremely simple affairs.

The resistance element of the potentiometer for the construction unit according to the invention is advantageously fitted to a sidewall of the housing disposed perpendicularly to the bottom. The ends of the resistance element may then be provided with blade-type contact springs inserted into the housing through slots disposed in the bottom and entering into further slots in the top of the housing so that they are retained parallel to the ends of the resistance element. The contact springs are provided with projections by means of which they are applied against the ends of the resistance element under tension. The ends of these contact springs also project from the bottom of the housing in a position parallel to the connecting studs so that together with these studs they may be soldered into a printed circuit, for example. A contact spring bearing against the rear wall of the housing from outside and, with a forked end, engaging a slot in the end of the tuning spindle projecting from the rear wall of the housing may also be used to retain the tuning spindle in its operative position. With an end extending parallel to the connecting studs this contact spring also projects through a slot in a section of the bottom of the housing projecting beyond the rear wall of the housing. In this extremely simple manner the tuning spindle is safely locked in the housing and simultaneously contacted, and this connection, too, may be soldered into a suitable circuit together with the other connecting wires and blades. In addition, the contact spring for the tuning spindle may project through a recess provided in the slide and thus simultaneously serve as stop for the rest position of the slide. Accordingly, the work involved in installing the tuning spindle and the associated pushbutton is essentially limited to inserting these two parts into the openings provided for the purpose in the walls of the housing and installing the contact spring engaging the end of the tuning spindle. It is obvious that with this embodiment of the invention assembly is reduced to a minimum.

For actuation of the tuning spindle, a tuning knob may be disposed on the front side of the housing concentrically to the tuning spindle and supported in a manner permitting it to be rotated and displaced in its longitudinal direction, said tuning knob being provided with a flange at the end facing the housing. This flange engages a transverse slot in the end of the slide projecting from the front wall of the housing. This positive connection between the flange and the slot forces the slide to follow the movement of the tuning knob when the latter is depressed so that the tuning knob together with the slide represents the pushbutton. Nevertheless, for control of the tuning spindle, the knob can readily be rotated with respect to the slide. In this arrangement, the tuning knob may be loaded by a helical compression spring which bears against the front wall of the housing and simultaneously serves as return spring for the slide. As a safeguard against inadvertent adjustments of the tuning spindle it is advisable to equip the tuning knob with a built-in coupling providing a positive rotary lock which will be operative only when the slide is in its depressed position.

Another embodiment of the invention provides for a flap to be hinged to the front side of the housing so that it covers the front side of the housing and its end, which is preferably provided with a web, is elastically seated against the end of the slide projecting from the front side of the housing. This flap functions like the key of a key set of the type frequently employed for communications equipment. The position of the flap is always determined by the fact that the flap seats against the slide so that in this arrangement, too, the slide may be locked and released, e.g. in the manner described above. Behind the flap, the end of the tuning spindle projecting from the front side of the housing may again be provided with a tuning knob, to which access is gained by lifting the flap. In a further embodiment of the invention, the tuning knob may be supported on the tuning spindle in a manner permitting it to be displaced in the longitudinal direction of said spindle and may be loaded by a spring which, when the flap is opened, moves the knob into a position where it can be gripped with ease.

Instead of the pressure mechanism mentioned above, mag netic means may be provided for retaining the key in its depressed position. Similar magnetic means are employed for the key suggested prior to this invention. However, with the key according to the present invention, an electromagnet with a spring-loaded plunger-type armature disposed perpendicularly to the slide which, under the action of the loading spring, enters into a recess in the top of the slide when the key is depressed is provided preferably at the back of the housing. In this manner, the slide is mechanically locked in the depressed position by the plunger type armature f the magnet, while a current impulse which retracts the plunger-type armature from the recess of the slide into the magnet coil so that the slide can return to its initial position under the action of the loading spring is sufficient to release the key. The sheet-metal yoke of the magnet may be provided with two lugs entering a slot provided in an extension of the bottom of the housing on either side of the slide. Additionally, the magnet may be retained by a flexible blade located at the top of the housing and provided with a detent tab extending into a corresponding recess of the magnet yoke. Both the extension of the housing bottom with the slot and the flexible blade may be injectionmoulded integral with the housing so that such a magnet may be added, whenever it is needed, by simple insertion. Furthermore, all slides may be provided with the recess described, irrespective of whether the mechanical locking arrangement with magnetic release or the pressure mechanism discussed above is employed. Accordingly, it is suflicient to install either the wire arm or an electromagnet in order to build a reset button or, alternatively, akey with electromagnetic release from the same initial components.

In a further embodiment of the invention, the construction unit may be provided with its own scale. This scale is advantageously formed by a flat coil spring, the woundup portion of which is arranged on a pin disposed in front of the front side of the housing and the end of which projects through a slot in the front wall of the housing and is hooked to the slider of the potentiometer. Such a scale combines the advantages of a very simple design with minimum space requirements and still provides sufficiently accurate indication for most purposes.

In a preferred embodiment of the invention, the aforementioned pin is disposed on a support with a foot which is inserted in a preferably dovetail-shaped slot in the top of the housing. Again, this dovetail-shaped slot may be injectionmoulded integral with the housing so that the same housing may be used for construction units with and without scales. In this arrangement, the support may be so designed as to form a casing enclosing the pin at least partially and featuring a viewing window for the scale formed by the flat coil spring. The above-mentioned flap may be hinged to the support for the flat coil spring, for example.

In order to enable any desired number of construction units to be combined into a tuner, the top of the housingmay be provided with a preferably dovetail-shaped slot for slipping the units onto a bus bar. Of course, the construction units may also be arranged separately, depending on what is the most suitable arrangement for the specific application, and for many applications it will be sufficient to position the construction units on a comparatively stiff plate of a printed circuit. In this case, correlation between the construction units and the various frequency bands must be provided for by a corresponding wiring of the switch contacts.

Further details and embodiments of the invention will become apparent from the following specification, in which the invention is described and explained in detail, reference being made to the embodiments shown by way of example in the accompanying drawing. In other embodiments of the invention, the features apparent from the specification and the drawing may be applied either individually or in any desired combination of a plurality of such features.

In the accompanying drawing:

FIG. 1 is the front view of a group of three construction units according to the invention combined on a bus bar,

FIG. 2 is a side elevation of the uppermost construction unit in FIG. 1 in the direction of the arrow II,

FIG. 3 is a view of the underside of a slide of such a construction unit along the line Ill-III in FIG. 2,

FIG. 4 is a side elevation of the slide according to FIG. 3 in the direction of the arrow IV,

FIG. 5 is a section through such a construction unit, taken along the line V-V in FIG. 1 near the sidewall of the housing,

FIG. 6 is a view of the housing according to FIG. 2 from below,

FIG. 7 is a rear elevation of the housing according to FIG. 2,

FIG. 8 is the side elevation of a further embodiment of the invention, and

FIG. 9 is a rear elevation of the construction unit according to FIG. 8.

The embodiments of the invention shown by way of example in the accompanying drawing, both feature a housing 1 made of plastic, which consists of a frame forming the bottom 2, the front wall 3, the rear wall 4, and the cover 5 of said housing, said frame being closed on one side by a sidewall 6. The inner surface of the sidewall 6 mounts the resistance layer 7 of a potentiometer, the slider 8 of which is disposed on a tuning spindle 9 supported in the front wall 3 and the rear wall 4 of the housing. The end of the tuning spindle 9 projecting through the rear wall 4 has a reduced diameter so that said spindle features a shoulder which bears against the inside of the rear wall 4. The end projecting through the rear wall is provided with an annular groove engaged by the forked end 10 of a contact spring 1 l, as shown in FIG. 7, the other end of said contact spring projecting through a corresponding slot in an extension 12 of the bottom of the housing projecting beyond the rear wall 4. In this very simple manner, the tuning spindle 9 is safely retained in the housing 1 and a proper contact with the spindle is ensured simultaneously. The end of the blade-type contact spring 11 projecting from the bottom 2 can readily be soldered into a printed circuit. Similar blade-type contact springs 13 and 14 supply current to the ends of the re sistance element 7 of the potentiometer. These contact springs are inserted from below in openings in the bottom 2 of the housing located in the immediate vicinity of the inner surface of the sidewall 6 of the housing. Corresponding openings, into which extend the other ends of the contact springs 13, are provided in the cover 5 of the housing. These other ends of the blade-type contact springs are secured by means of pins 15 (see FIG. 5). In their central area, said contact springs 13 and 14- are provided with projecting contact points 16 by means of which they contact the ends of the resistance element 7 under tension. The ends 13 and 14 projecting from the bottom 2 of the housing are also capable of being directly soldered into a printed circuit.

Additionally, the housing 1 accommodates a sliding-type switch enabling switches to be opened and closed by pressing a button or key in order toconnect the potentiometer to a tuned circuit and initiate further switching operations, if desired. For this purpose, a slide 21 is provided, which is formed by an elongated plastic injection moulding of substantially rectangular cross section projecting through corresponding openings in the front wall 3 and the rear wall 4 of the housing and resting against the inside of the bottom 2 of the housing. As may be noted from FIG. 3, recesses 22, into which V shaped leaf springs 23 are inserted in an upright position, are provided in that surface of the slide 21 which faces the bottom 2. At their apices, these springs are restrained between the cross-webs 24 forming boundary surfaces of said recesses 22 and pin-type projections 25 located adjacent to said crosswebs 22, while their legs project through slots 26 in webs 27 defining said recesses 22 laterally. The ends of the legs of these V-shaped leaf springs are provided with retaining tabs 28 bent off in an inward direction and engaging said webs 27 at their inner surfaces at the far end of the associated slots 26 with respect to the apices of said springs 23.

The leaf springs 23 cooperate with contact studs 29 and 30 inserted in the bottom 2 of the housing in two rows extending parallel to the slide 21 and projecting a short distance into the housing. The distance between the studs 29 and 30 is such that the slide portion accommodating the leaf springs 23 fits between the studs with the webs 27 so that in one positionthe inner ends of the studs 29 and 30 arranged in opposite pairs will be connected through the contact springs 23 which will contact the ends of the studs 29 and 30 with their portions projecting from the slots 26 in the webs 27. In another position, the same springs are located between the studs so that the electrical connection is interrupted. It is obvious that in one position of the slide one or more pairs of studs may be connected while the others are not connected and that connection may be interrupted between the first-mentioned pairs of studs and established between the pairs of studs mentioned in second place by changing the position of the slide.

During assembly, the slide is simply inserted into the housing from the front. It will then be retained in its position by the blade-type contact spring 11, which also serves to securethe tuning spindle 9 and projects through a recess 31 in the slide. The slide is normally loaded by a spring which tends to push the slide out of the housing in a forward direction. For this reason, the rear flank of the opening 31 seats against the contact spring 11 when the slide is in its rest or neutral position.

In the embodiment of the invention according to FIGS. 1 to 7 the slide operates on the principle of a reset button and is provided with an appropriate pressure mechanism by means of which the slide may be moved from its restposition into an operative position and locked in that position by depressing the button or key and by means of which it may be unlocked again when the button or key is pressed a second time so that the initial position is restored by the force exerted by the spring. In the embodiment of the invention shown by way of example in the accompanying drawing, a swivable arm 33, which is simply formed by a piece of wire the two ends of which are bent off in opposite directions, is provided .for this purpose on the outside of a web 32 of the slide 21 extending over the row of studs 29 adjacent to the sidewall 6 of the housing. One end of this piece of wire is inserted in a correspond ing bore in the outside of the slide 21, as shown in FIGS. 3 and 4. The arm 33 extends from its pivot towards the front end of 'the slide, while the sidewall 6 ol'the housing is provided with a control cam 34, integral with said sidewall of the housing, into which extends the end 35 of the arm 33 projecting from the :slide. The control cam 34 features a heart-shaped section 36 with a dent 37 in which the bent-off end 35 of the arm 33 is caught when the button or key is depressed. When the button or key is pressed a second time, said bent-off end 35 of the arm 33 is returned from this dent to the straight section of the control cam 34. In this manner, the slide, which is initially in a position of rest, in which the rear edge of the opening 31 is seated against the rear side of the blade-type contact spring 11 under the force exerted by a spring, may be pressed into, and caught in, a locking position, from which it may be released again when the button or key is pressed a second time, whereupon the button or key will be returned to its initial position by means of the spring.

In the embodiment of the invention shown by way of example in FIGS. 2 to 7, a positive connection exists between the end of the slide 21 projecting from the front wall 3 of the housing and a control knob 41 rotatably supported on a tubular extension 42 on the front wall 3 of the housing in a position concentric to the tuning spindle 9. This tubular extension is surrounding by a helical compression spring 43 which bears against the front side of the housing at one end and against a shoulder in said knob 41 at the other end. The end of the knob 41 facing the front wall 3 of the housing is provided with a flange 45 engaging a corresponding transverse slot 46 at the front end of the slide 21. Consequently, when the knob 41 is pressed, the slide 21 will move aft together with the knob until the slide is locked in its depressed position and arrests the knob in this depressed position. In this position, a coupling incorporated in the knob and not shown in detail in the accompanying drawing provides a positive rotary connection between the knob 41 and the tuning spindle 9 so that the setting may now be changed by rotating the knob. When the knob 41 is pressed a second time, the slide 21 will be unlocked again and the knob together with the slide will be returned to the initial position by means of the spring 43.

Furthermore, the embodiment of the invention shown by way of example in FIGS. 1 to 7 is provided with a scale formed by a flat coil spring, the woundup portion 51 of which is arranged on a pin 52 located above the knob 41 in frontof the front side of the housing. The pin 52 is attached to a support 53 featuring a dovetail-shaped foot 54 inserted in a corresponding slot in the top of the housing 1. The end 55 of the flat coil spring projects through a corresponding slot in the front wall 3 of the housing and is secured to a hook 56 provided for this purpose on the potentiometer slider 8 disposed on the tuning spindle 9. It will be noted that the construction unit according to FIGS. 1 to 6 may be used partly with or without such a scale. The extra costs involved in fabricating the housing with the slide for the foot 54 of the support 53 and of providing the slider 8 with the hook 56, irrespective of whether these elements will be needed or not, are negligible.

In the embodiment of the invention shown by way of example in FIGS. 8 and 9, the construction unit is provided with a key with electromagnetic release instead of a reset button. Accordingly, theswivable arm 33 was omitted on the slide 21. Instead, an electromagnet 62 featuring a plunger-type armature '63 which can move perpendicularly to the slide 21 was arranged between the aft extension 12 of the bottom of the housing and a flexible blade 61 at the top of the housing. At the side facing the armature 63 of the magnet, the slide is provided with a flat recess 64 forming an extension of the opening 31, as shown by the dash lines in FIG. 3, into which the plunger-type armature 63 enters under the action of its loading spring when the slide is moved into the depressed position. To release the slide, the magnet 62 must be excited so that the plunger-type armature 63 is retracted from the recess 64 and the slide can be returned to its initial position by means of a spring. A legged spring 65 is provided for this purpose in the embodiment of the invention shown by way of example in FIGS. 8 and 9. One leg of this spring enters into the rear wall 4 of the housing while the other leg bears against a projection of the slide.

The magnet 62 is simply clamped in position at the end of the housing 1 and securely retained in its position owing to the fact that its sheet-metal yoke 66 is extending by two lugs 67 engaged by slots in the extension 12 of the bottom of the housing on either side of the slide 21, while a detent tab provided on the side of the blade 61 facing the magnet yoke is engaged by a corresponding recess of the magnet yoke 66. It is apparent that the mechanical locking arrangement may readily be substituted for the magnetic lock and that the flexible blade 61 and the detent slots in the extension 12 may be incorporated in each and every housing of such a construction unit so as to provide from the start for various kinds of future use.

A further difference between the embodiment of the invention shown by way of example in FIGS. 8 and 9 and the embodiment discussed before lies in the fact that the pin 51 supporting the flat coil spring 52, which serves as a scale, is enclosed in a casinglike box 71 provided with a viewing window for the scale in its front side. ln addition, a flap 72, which with a web 74 disposed at its outer edge is applied against the end face of the slide 21 by the force exerted by a leaf spring 73, is hinged to the support for the flat coil spring. The flap 72 serves as a key by means of which the slide 21 may be moved from its rest position into the depressed position. The flap 72 completely covers the entire front face of the construction unit, This flap also hides a tuning knob 75 supported on the outer end of the tuning spindle 9 in a manner permitting it to be displaced longitudinally while preventing rotation. The tuning knob is loaded by a helical compression spring 76 which pushes the knob outward when the flap 72 is lifted to gain access to the knob. The knob 75 may consist of a plurality of telescoping components in order to make the distance by which the knob 75 will project after the flap 72 has been lifted as long as possible so that the knob may be gripped more conveniently for greater ease of tuning. It shall be understood that the present invention is not restricted to the embodiment shown by way of example and that deviations from this embodiment are possible without exceeding the scope of the invention. In particular, the present invention includes all variations resulting from a combination of mechanical or electromagnetic release facilities, the optional use of a scale, the coupling of the slide to the tuning knob, or the provision of a flap. Furthermore, the construction units may be employed individually in any desired arrangement or positioned on a bus bar 77, s shown in H6. 1, which may be inserted in a dovetailshaped slot 78 provided in the top of the housing 1.

Having thus fully described our invention, what we claim as new and wish to secure by Letters Patent is:

1. A modular potentiometer-switch unit for tuners of HF communication equipment, particularly television and radio receivers, comprising:

a housing having a bottom, a cover, a rear wall, a front side and sidewalls;

a potentiometer disposed within said housing, formed of a resistance element, a pair of leads for external connection thereto and a slider associated therewith;

a tuning spindle, supported within said housing, on which said potentiometer slider slidably engages said resistance element;

a pushbutton switching element extending along the bottom of said housing parallel to said tuning spindle, said pushbutton switching element comprising:

a slide having a front end and a rear end,

a plurality of first webs arranged along the length of said slide and,

a plurality of contact springs each disposed along the length of said slide alternately with said first webs;

a plurality of connecting studs exposed on said housing along the bottom thereof in rows parallel to said pushbutton switch, whereby said contact springs releasably connect adjacent pairs of said connectingstuds by the action of said slide; and

means for engaging said pushbutton switch with said tuning spindle, whereby said tuning spindle is rotated by said means, so that said leads of said potentiometer and said connecting studs are selectively connected to tuning circuitry external of said housing while being controlled by said modular potentiometer switch.

2. A modular potentiometer-switch unit according to claim 1, wherein said slide contains a plurality of recesses opening toward said bottom of said housing, in which said contact springs are situated and wherein said contact springs are in the form of essentially Vshaped leaf springs, situated on edge in said recesses, said leaf springs being retained at their apices and projecting with the ends of their legs through slots in said first webs, whereby said first webs form the boundaries of said recesses.

3. A modular potentiometer-switch unit according to claim 1, wherein at least one edge of said slide is provided with a second web extending over a row of said studs, and further including a pressure mechanism disposed between the outer surface of said second web in the adjacent wall of said housing, and wherein said engaging means includes a spring, whereby said pressure mechanism locks said slide in its depressed position against the force exerted by said spring and releases it when pressed again. 4

4. A unit according to claim 3, characterized in that an arm is pivoted on the outside of said slide, said arm extending from its pivot towards the front end of said slide and featuring an outward projection at its free end, said projection being engaged by a guide slot in the form of a heart-shaped curve provided in said sidewall of said housing.

5. A unit according to claim 4, characterized in that said arm is formed by a piece of wire having its two ends bent off in opposite directions, one of said bent-off ends being engaged by a bore provided in said second web of said slide and the other by said guide slot.

6. A unit according to claim 1, characterized in that the resistance element is arranged on a sidewall of said housing disposed perpendicular to said bottom and in that blade-type contact springs bear against the ends of said resistance element, said contact springs being inserted in said housing through slots provided in said bottom and entering into further slots provided in the cover of said housing so that said contact springs are retained parallel to the ends of said resistance element and, with a projection, are applied against said ends of said resistance element under tension, and in that the ends of said contact springs project from said bottom of the housing parallel to said connecting studs.

7. A unit according to claim 1, characterized in that the tuning spindle is retained in its operative position by a blade-type contact spring, said blade-type contact spring bearing against the rear wall of the housing from outside and, with a slotted fork-type end engaging a slot provided in the end of said tuning spindle projecting from said rear wall of the housing and in that an end of said blade-type contact spring extending parallel to said connecting studs projects through a slot in a section of the bottom of the housing projecting beyond said rear wall.

8. A unit according to claim 7, characterized in that said blade-type contact spring for said tuning spindle projects through an opening provided in said slide and simultaneously serves as the stop for the rest position of said slide.

9. A unit according to claim 1, characterized in that said engaging means comprises a tuning knob disposed on the front side of said housing, concentric with said tuning spindle and supported in a manner permitting said tuning knob to be rotated and displaced in its longitudinal direction, and that said knob, at its end facing the housing, is provided with a flange engaging a transverse slot provided in the end of said slide projecting from said front wall of said housing.

10. A unit according to claim 9, characterized in that said tuning knob is loaded by a helical compression spring bearing against said front wall of said housing, said helical compression spring simultaneously serving as return spring for said slide.

11. A unit according to claim 9, characterized in that a built-in coupling provides a positive rotary lock between said tuning knob and said tuning spindle in the depressed position of said slide only.

12. A unit according to claim 1, characterized in that a flap is provided at said front side of said housing, said flap covering said front side of said housing and being elastically seated with its end, which is preferably provided with a web, against the end of said slide projecting from said front side of said housmg.

13. A unit according to claim 12, characterized in that a tuning knob is disposed behind said flap on the end of said tuning spindle projecting from said front side of said housing, said tuning knob being accessible after said flap has been lifted.

14. A unit according to claim 13, characterized in that said tuning knob is so supported on said tuning spindle that it may be displaced in the longitudinal direction of said spindle and in that said tuning knob is loaded by a spring moving said knob into a position where it may be gripped with ease after said flap has been opened.

15. A unit according to claim 1, characterized in that an electromagnet with a spring-loaded plunger-type armature disposed perpendicularly to said slide is provided at the rear of said housing, said plunger-type armature entering into a recess provided in the top of said slide under the force exerted by its loading spring when the key is depressed.

16. A unit according to claim 15, characterized in that said magnet has a sheet-metal yoke provided with two lugs engaged by a slot provided in an extension of the bottom of the housing on each side of said slide and in that a flexible blade having a detent tab is provided at the top of said housing, said detent tab of said flexible blade being engaged by a corresponding recess of said magnet yoke.

17. A unit according to claim 12, characterized in that said unit is provided with a scale formed by a flat coil spring having a wound-up section, which is located on a pin arranged in front of the front side of said housing and the end of which projects through a slot in the front wall of said housing and is hooked to the slider of the potentiometer.

18. A unit according to claim 17, characterized in that said pin is disposed on a support with a foot inserted in a dovetailshaped slot provided in the top of said housing.

19. A unit according to claim 18, characterized in that said support takes the form of a casing, said casing enclosing said pin at least partially and featuring a viewing window for the scale formed by said flat coil spring.

20. A unit according to claim 18, characterized in that said flap is hinged to said support for said flat coil spring.

21. A unit according to claim 20, characterized in that the top of said housing is provided with a preferably dovetailshaped slot to receive a connection bar.

22. A unit according to claim 21, characterized in that said housing and said slide are constructed of plastic. 

1. A modular potentiometer-switch unit for tuners of HF communication equipment, particularly television and radio receivers, comprising: a housing having a bottom, a cover, a rear wall, a front side and sidewalls; a potentiometer disposed within said housing, formed of a resistance element, a pair of leads for external connection thereto and a slider associated therewith; a tuning spindle, supported within said housing, on which said potentiometer slider slidably engages said resistance element; a pushbutton switching element extending along the bottom of said housing parallel to said tuning spindle, said pushbutton switching element comprising: a slide having a front end and a rear end, a plurality of first webs arranged along the length of said slide and, a plurality of contact springs each disposed along the length of said slide alternately with said first webs; a plurality of connecting studs exposed on said housing along the bottom thereof in rows parallel to said pushbutton switch, whereby said contact springs releasably connect adjacent pairs of said connecting studs by the action of said slide; and means for engaging said pushbutton switch with said tuning spindle, whereby said tuning spindle is rotated by said means, so that said leads of said potentiometer and said connecting studs are selectively connected to tuning circuitry external of said housing while being controlled by said modular potentiometer switch.
 2. A modular potentiometer-switch unit according to claim 1, wherein said slide contains a plurality of recesses opening toward said bottom of said housing, in which said contact springs are situated and wherein said contact springs are in the form of essentially V-shaped leaf springs, situated on edge in said recesses, said leaf springs being retained at their apices and projecting with the ends of their legs through slotS in said first webs, whereby said first webs form the boundaries of said recesses.
 3. A modular potentiometer-switch unit according to claim 1, wherein at least one edge of said slide is provided with a second web extending over a row of said studs, and further including a pressure mechanism disposed between the outer surface of said second web in the adjacent wall of said housing, and wherein said engaging means includes a spring, whereby said pressure mechanism locks said slide in its depressed position against the force exerted by said spring and releases it when pressed again.
 4. A unit according to claim 3, characterized in that an arm is pivoted on the outside of said slide, said arm extending from its pivot towards the front end of said slide and featuring an outward projection at its free end, said projection being engaged by a guide slot in the form of a heart-shaped curve provided in said sidewall of said housing.
 5. A unit according to claim 4, characterized in that said arm is formed by a piece of wire having its two ends bent off in opposite directions, one of said bent-off ends being engaged by a bore provided in said second web of said slide and the other by said guide slot.
 6. A unit according to claim 1, characterized in that the resistance element is arranged on a sidewall of said housing disposed perpendicular to said bottom and in that blade-type contact springs bear against the ends of said resistance element, said contact springs being inserted in said housing through slots provided in said bottom and entering into further slots provided in the cover of said housing so that said contact springs are retained parallel to the ends of said resistance element and, with a projection, are applied against said ends of said resistance element under tension, and in that the ends of said contact springs project from said bottom of the housing parallel to said connecting studs.
 7. A unit according to claim 1, characterized in that the tuning spindle is retained in its operative position by a blade-type contact spring, said blade-type contact spring bearing against the rear wall of the housing from outside and, with a slotted fork-type end engaging a slot provided in the end of said tuning spindle projecting from said rear wall of the housing and in that an end of said blade-type contact spring extending parallel to said connecting studs projects through a slot in a section of the bottom of the housing projecting beyond said rear wall.
 8. A unit according to claim 7, characterized in that said blade-type contact spring for said tuning spindle projects through an opening provided in said slide and simultaneously serves as the stop for the rest position of said slide.
 9. A unit according to claim 1, characterized in that said engaging means comprises a tuning knob disposed on the front side of said housing, concentric with said tuning spindle and supported in a manner permitting said tuning knob to be rotated and displaced in its longitudinal direction, and that said knob, at its end facing the housing, is provided with a flange engaging a transverse slot provided in the end of said slide projecting from said front wall of said housing.
 10. A unit according to claim 9, characterized in that said tuning knob is loaded by a helical compression spring bearing against said front wall of said housing, said helical compression spring simultaneously serving as return spring for said slide.
 11. A unit according to claim 9, characterized in that a built-in coupling provides a positive rotary lock between said tuning knob and said tuning spindle in the depressed position of said slide only.
 12. A unit according to claim 1, characterized in that a flap is provided at said front side of said housing, said flap covering said front side of said housing and being elastically seated with its end, which is preferably provided with a web, against the end of said slide projecting from said front side of said housing.
 13. A unit according to claim 12, characterized in that a tuning knob is disposed behind said flap on the end of said tuning spindle projecting from said front side of said housing, said tuning knob being accessible after said flap has been lifted.
 14. A unit according to claim 13, characterized in that said tuning knob is so supported on said tuning spindle that it may be displaced in the longitudinal direction of said spindle and in that said tuning knob is loaded by a spring moving said knob into a position where it may be gripped with ease after said flap has been opened.
 15. A unit according to claim 1, characterized in that an electromagnet with a spring-loaded plunger-type armature disposed perpendicularly to said slide is provided at the rear of said housing, said plunger-type armature entering into a recess provided in the top of said slide under the force exerted by its loading spring when the key is depressed.
 16. A unit according to claim 15, characterized in that said magnet has a sheet-metal yoke provided with two lugs engaged by a slot provided in an extension of the bottom of the housing on each side of said slide and in that a flexible blade having a detent tab is provided at the top of said housing, said detent tab of said flexible blade being engaged by a corresponding recess of said magnet yoke.
 17. A unit according to claim 12, characterized in that said unit is provided with a scale formed by a flat coil spring having a wound-up section, which is located on a pin arranged in front of the front side of said housing and the end of which projects through a slot in the front wall of said housing and is hooked to the slider of the potentiometer.
 18. A unit according to claim 17, characterized in that said pin is disposed on a support with a foot inserted in a dovetail-shaped slot provided in the top of said housing.
 19. A unit according to claim 18, characterized in that said support takes the form of a casing, said casing enclosing said pin at least partially and featuring a viewing window for the scale formed by said flat coil spring.
 20. A unit according to claim 18, characterized in that said flap is hinged to said support for said flat coil spring.
 21. A unit according to claim 20, characterized in that the top of said housing is provided with a preferably dovetail-shaped slot to receive a connection bar.
 22. A unit according to claim 21, characterized in that said housing and said slide are constructed of plastic. 